Well, I finally found my books (not in the closet under the stairs after all, but in my dad's garage). The illustration isn't even of Caspian's cabin, but of the cabin that Edmond and Eustace will now share with Caspian since he is giving his cabin to Lucy. And, the globe is definitely a terrestial, rather than celestial, globe. Illustrator error, plain and simple.
It did spark some very interesting conversation though, didn't it? And it got my CON back within reach, so I know what I'll be reading this weekend. :D